**Background:** Socioeconomic disparities are known to affect child brain development, but the extent to which household- and neighborhood-level socioeconomic factors contribute to racial differences in brain outcomes remains unclear. This study used the ABCD dataset to isolate specific socioeconomic characteristics associated with adverse brain outcomes in preadolescents.
**Methods:** The authors performed a cross-sectional analysis of 9,638 children aged 9–10 years from the ABCD baseline dataset (v.2.0.1). Cognitive performance was assessed using the NIH Toolbox cognitive battery (Fluid Composite, Crystallized Composite, Total Cognition Composite, and Oral Reading Recognition). Cortical morphometric measures (thickness, area, volume) were derived from T1-weighted MRI using a Freesurfer-based pipeline with the Destrieux atlas (74 cortical and subcortical regions per hemisphere). Neighborhood socioeconomic characteristics were measured using the Area Deprivation Index (ADI) percentile and five additional neighborhood indicators selected via a feature selection algorithm (CAR scores). Linear mixed effects models incorporated random effects for site/scanner and family ID, with fixed effects including age, sex, and parental education. Serial mediation analysis tested whether household income (m1) and neighborhood socioeconomic indicators (m2) mediated racial differences in cognitive and brain outcomes.
**Key Results:** Complete data were available for 9,638 children (55% White, 13% Black, 20% Hispanic; 53% male). Higher ADI percentile predicted poorer Total Cognition Composite scores and smaller total cortical volume across all income tiers. Of the 664 children from the most impoverished neighborhoods (ADI >90th percentile), 482 (72.6%) were Black/Hispanic and only 92 (13.8%) were White. Conversely, among households earning >$200,000, 75.7% were White and 8.9% were Black/Hispanic. The Total Cognition Composite score was 7.3 points lower (95% CI, 6.5–8.1) in Black vs. White children in the lowest income tier (<$50,000), but this gap diminished by ~40% to 4.4 points (95% CI, 3.0–5.8) in the highest income tier (>$100,000). Reading score differences between Black and White children (3.7 points; 95% CI, 2.0–4.4) were fully offset in the high-income group (1.3 points; 95% CI, 0.0–2.3). The strongest direct effects on brain volumes were for ADI, percentage with high school education, percentage of single-parent households, and median household income, with the most pronounced effect for total cortical volume (ΔR²=1.7%, Q<10⁻³⁷). Regionally, the superior frontal gyrus showed the greatest mediation effect for household income (Z=7.48, Q<0.001), while neighborhood-level disparities were most associated with volumes of the left cuneus (% single parent households, Z=7.86, Q<0.001), supramarginal gyrus (% unemployed, Z=6.02, Q<0.001), and right parietooccipital sulcus (% with at least high school education, Z=5.30, Q<0.001).
**Clinical Implications:** This study demonstrates that socioeconomic characteristics of the home and neighborhood are negatively associated with preadolescent brain outcomes, with Black and Hispanic children disproportionately exposed to these disadvantages. Higher household income partially mitigates racial differences in cognitive scores, but neighborhood-level disparities persist even among high-income minority families. The findings highlight the need for policy interventions—such as community resource allocation, housing support, and income assistance—to address socioeconomic determinants of brain development. The authors note that the cross-sectional design precludes causal inference, and the ABCD cohort over-represents higher-income families, potentially limiting generalizability to rural populations.